Development of a 3-Dimensional Finite Element Model of Air Bag Deployment and Interactions with an Occupant Using DYNA3D

In recent years supplemental inflatable restraint systems (airbags) have been installed in motor vehicles to mitigate driver/front passenger harm in vehicle frontal crashes. The performance of the airbag and the level of protection it provides the occupant can be evaluated by a combination of experimental and analytical techniques. Analytical modeling of airbag inflation is desirable in automotive design, particularly when the technique encompasses the airbag, occupant and vehicle structure in an integrated system.

This paper is concerned with the development of nonlinear finite element (FE) technology to simulate airbag deployment and its interaction with an articulated occupant model. This technology is being developed in the dynamic large deformation Lagrangian based DYNA3D code which has been successfully used in vehicle crashworthiness simulations. The airbag material was simulated by an orthotropic “wrinkle free” membrane elastic model. A simplified gas model based on assuming uniform thermodynamic properties (pressure, density, temperature and internal energy) throughout the airbag was coupled to the airbag structure. New developments included inflation of an unfolded airbag and predicting its deployment kinematics and identifying its contact and interactions with several spherical and flat surfaces. The predicted bag deformations and contact forces compared favorably with corresponding experimental data. In addition, an attempt was made to simulate the deployment and interactions of a folded airbag with a hybrid III dummy model.